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Seismic performance of stainless-steel built-up box columns subjected to constant axial loads and cyclic lateral deformations
, Article Structures ; Volume 33 , 2021 , Pages 4080-4095 ; 23520124 (ISSN) ; Sadrara, A ; Jalali, S. R ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The seismic behavior of stainless-steel built-up box columns subjected to constant axial loads and cyclic lateral deformation that are used in special moment frames (SMFs) has been investigated through finite element (FE) analysis. A total of 208 numerical models were conducted to cover a range of parameters affecting the seismic behavior of the columns. These include the web slenderness ratio, flange slenderness ratio, global slenderness ratio, axial load level, and lateral loading protocol. The performance indices of overstrength factor, axial shortening, out-of-plane deformation, plastic hinge length, and rotation capacity were calculated and compared. Local buckling of the columns also...
Evaluation of strong column-weak beam criterion in spliced columns of steel moment frames
, Article Results in Engineering ; Volume 14 , 2022 ; 25901230 (ISSN) ; Maleki, S ; Sharif University of Technology
Elsevier B.V
2022
Abstract
In the seismic design of steel special moment frames, it is necessary to ensure that columns are generally stronger than beams. This reduces the probability of a weak story failure mechanism of the frame and ensures the formation of beams' plastic hinges earlier than the columns'. This criterion is known as strong column-weak beam (SCWB) in seismic design codes and is checked by a formula in the form of a ratio of total flexural strengths of columns to beams framing at each joint. It is common practice to ignore the column section change at the splice location and to use the flexural strength of the larger column section in evaluating this ratio. In this paper, several steel special moment...
Collapse assessment of steel moment frames using endurance time method
, Article Earthquake Engineering and Engineering Vibration ; Volume 14, Issue 2 , 2015 , Pages 347-360 ; 16713664 (ISSN) ; Estekanchi, H. E ; Sharif University of Technology
Institute of Engineering Mechanics (IEM)
2015
Abstract
In endurance time (ET) method structures are subjected to a set of predesigned intensifying excitations. These excitations are produced in a way that their response spectrum, while complying with a specified spectrum, intensifies with time so they can be used approximately to simulate the average effects of several ground motions scaled to different intensities. In this paper applicability of the ET method for evaluating collapse potential of buildings is investigated. A set of four steel moment frames is used for collapse assessment. The process of using ET method in collapse evaluation is explained and the results are compared with incremental dynamic analysis (IDA) results. It is shown...
Damage estimation of steel moment-resisting frames by endurance time method using damage-based target time
, Article Journal of Earthquake Engineering ; 2017 , Pages 1-30 ; 13632469 (ISSN) ; Estekanchi, H. E ; Sharif University of Technology
Taylor and Francis Ltd
2017
Abstract
In endurance time method, seismic performance of structures under artificial intensifying accelerograms is investigated. In this method, the time duration of excitation (target time) will be assigned on the basis of linear response spectra. Damage spectra, which are the variation of a damage index versus the system period, can be used effectively to modify the target time of the excitations. In this research, various damage indices for a number of steel moment frames are estimated using the endurance time method with two types of target time, and the results are compared with those corresponding to the scaled real earthquakes. It is observed that damage estimation of the frames via the...
Damage estimation of steel moment-resisting frames by endurance time method using damage-based target time
, Article Journal of Earthquake Engineering ; Volume 22, Issue 10 , 2018 , Pages 1806-1835 ; 13632469 (ISSN) ; Estekanchi, H. E ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
In endurance time method, seismic performance of structures under artificial intensifying accelerograms is investigated. In this method, the time duration of excitation (target time) will be assigned on the basis of linear response spectra. Damage spectra, which are the variation of a damage index versus the system period, can be used effectively to modify the target time of the excitations. In this research, various damage indices for a number of steel moment frames are estimated using the endurance time method with two types of target time, and the results are compared with those corresponding to the scaled real earthquakes. It is observed that damage estimation of the frames via the...
Analytical study of special girder moment frames using a mixed shear-flexural link element
, Article Canadian Journal of Civil Engineering ; Volume 34, Issue 9 , 2007 , Pages 1119-1130 ; 03151468 (ISSN) ; Erfani, S ; Sharif University of Technology
2007
Abstract
The present paper introduces a mixed shear-flexural (VM) link element that is capable of modelling shear yielding, flexural yielding, and their interaction under monotonic and cyclic loadings. The inelastic deformations are modelled using the multisurfaces approach with dissimilar yield surfaces and a stiffness matrix with nonzero off-diagonal components in shear-flexural space. A new kinematic hardening and new non-associated flow rules are employed. A special girder, which has an open web in the middle, is introduced and modelled using the developed VM link element. It is shown that the results of analyses using the VM link element are in good agreement with those from a finite element...
Evaluation of vierendeel peripheral frame as supporting structural element for prevention of progressive collapse
, Article Steel and Composite Structures ; Volume 26, Issue 5 , March , 2018 , Pages 549-556 ; 12299367 (ISSN) ; Omidi, H ; Sharif University of Technology
Techno Press
2018
Abstract
Progressive building collapse occurs when failure of a structural component leads to the failure and collapse of surrounding members, possibly promoting additional failure. Global system collapse will occur if the damaged system is unable to reach a new static equilibrium configuration. The most common type of primary failure which led to the progressive collapse phenomenon, is the sudden removal of a column by various factors. In this study, a method is proposed to prevent progressive collapse phenomena in structures subjected to removal of a single column. A vierendeel peripheral frame at roof level is used to redistribute the removed column’s load on other columns of the structure. For...
Design of Soft Story in Reinforced Concrete Structures Due to Removal of Masonry Infill Walls
, M.Sc. Thesis Sharif University of Technology ; Golafshani, Ali Akbar (Supervisor) ; Tabeshpour, Mohammad Reza (Supervisor)
Abstract
In past few decades researchers and engineers have researched extensively on the effects of masonry infill walls in structural frames and the effects of masonry infill walls on the structural response was a concern for them. Since used materials and therefore the strength and stiffness of these walls are extremely depends on construction site and available mate-rials, according to geographical conditions most of countries inserted their own rules for considering effects of masonry infill walls in their codes and standards. Our country, Iran was not excepted from this regularity and in past few years the effect of existence of ma-sonry infill walls in structural response has been considered...
Effect of Reduction in Behavior Factor on Steel Structures and their Dimensions
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
As you know, the behavior factor is one of the important parameters and values for calculating earthquake force and base cutting in the building. In this research, the effect of coefficient of behavior (R) on metal structures has been investigated. For this purpose, we selected a metal structure with an average bending frame and dual system with shear wall and examined it. To determining the effect of this coefficient on different structures, we modeled the structures with regular and irregular plans. Considering the structure height effect and also the type of soil on the site of the proposed structure to the factor and refractive coefficient (B) and its direct impact on the magnitude of...
Estimating structural damage of steel moment frames by Endurance Time method
, Article Journal of Constructional Steel Research ; Volume 64, Issue 2 , 2008 , Pages 145-155 ; 0143974X (ISSN) ; Arjomandi, K ; Vafai, A ; Sharif University of Technology
2008
Abstract
In Endurance Time (ET) method, structures are subjected to gradually intensifying accelerograms and their performance is judged based on the maximum time duration in which they can satisfy the predefined endurance criteria. Damage indexes are used in ET method as the endurance criteria. In this paper, correlation between the values of various damage indexes as obtained from nonlinear time-history analysis of steel moment frames subjected to scaled earthquakes are compared with those from ET method at the same level of spectral acceleration. It is shown that the average value of various damage indexes can be estimated from ET analysis results. Advantages, accuracy and limitations of this...
Machine learning-based seismic damage assessment of non-ductile RC beam-column joints using visual damage indices of surface crack patterns
, Article Structures ; Volume 45 , 2022 , Pages 2038-2050 ; 23520124 (ISSN) ; Mansourdehghan, S ; Asjodi, A. H ; Dolatshahi, K. M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
After a significant earthquake, the updated status of the structural elements is usually determined based on a qualitative visual inspection. Although visual inspection provides a prompt assessment of the damaged elements, the output of this subjective method is influenced by the experience and decision of a trained inspector, which may vary from case to case. In this study, an innovative machine learning-based procedure is developed to automate damage state identification of non-ductile reinforced concrete moment frames (RCMFs) utilizing visual indices of crack patterns of the concrete surface. An extensive database including 264 surface crack patterns is constructed corresponding to 61...
Endurance time method for multi-component analysis of steel elastic moment frames
, Article Scientia Iranica ; Volume 18, Issue 2 A , 2011 , Pages 139-149 ; 10263098 (ISSN) ; Estekanchi, H. E ; Sharif University of Technology
Abstract
The Endurance Time (ET) method is a time history-based dynamic analysis procedure which uses special intensifying acceleration functions for evaluation of the seismic response of structures. One of the potential applications of the ET method is in the three-dimensional analysis of buildings under multidirectional excitations. In this paper, considering horizontal components of excitation, an algorithm for the multi-component analysis of building structures by the ET method is proposed, and results of the ET method for various steel moment frames with 1 to 7 stories are compared with results from time history analysis with real earthquakes. Results show that based on recommendations of...
Assessment of collapse modes in reinforced concrete frames considering record-to-record and modeling uncertainties
, Article Scientia Iranica ; Volume 24, Issue 5 , 2017 , Pages 2213-2226 ; 10263098 (ISSN) ; Pourzeynali, S ; Estekanchi, H. E ; Sharif University of Technology
Abstract
Dominant Collapse Mechanisms (DCMs) have been reported to play an important role in collapse capacity of structural systems and the seismic losses consequent to it. Therefore, DCMs of Reinforced Concrete (RC) frames have been studied, in this article, considering Record-To-Record (RTR) and modeling uncertainties. Two sets of RC frames have been designed, in this regard, that share the design assumptions but contain different levels of over-strength. Each set contains 26, 4- to 20-story nonlinearly modeled frames. Initially, Incremental Dynamic Analysis (IDA) was used to identify frames' DCMs. Then, the RTR variability reflected through IDA was combined with spectral shape and pulse effects...
Seismic behavior of concrete moment frame reinforced with GFRP bars
, Article Composites Part B: Engineering ; Volume 163 , 2019 , Pages 324-338 ; 13598368 (ISSN) ; Khaloo, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this research, four types of concrete moment frame were designed with glass fiber reinforced polymer (GFRP) bars according to ACI 440.1R-15 and the seismic behavior was assessed using pushover analysis. The frames were three and five stories with two and three bays. A computer code was developed to calculate the amount of fiber reinforced polymer bars in beams of the frames. In order to evaluate nonlinear behavior in plastic hinge regions, sections of beams and columns were analyzed on the basis of moment-curvature diagram and also P-M interaction curve for columns. Performance levels of frames were determined considering ATC-40 criteria. Behavior of concrete moment frames reinforced with...
Machine learning-aided scenario-based seismic drift measurement for RC moment frames using visual features of surface damage
, Article Measurement: Journal of the International Measurement Confederation ; Volume 205 , 2022 ; 02632241 (ISSN) ; Mansourdehghan, S ; Asjodi, A. H ; Dolatshahi, K.M ; Sharif University of Technology
Elsevier B.V
2022
Abstract
This paper presents a novel computer vision-based methodology for assessment of the seismic damage in reinforced concrete moment frames using visual characteristics of surface damage following an earthquake. An extensive collected database comprising 974 images associated with 256 cyclic-loaded damaged beam-column joints, providing a set of cracking and crushing progression with increasing the evolution of damage level, is collected and used for the development and validation of the methodology. Employing image processing techniques, the characteristics of the surface damage, including the cracking length and crushing areas, are measured and used in a scenario-based assessment for the...
Peak drift ratio estimation for RC moment frames using multifractal dimensions of surface crack patterns
, Article Engineering Structures ; Volume 255 , 2022 ; 01410296 (ISSN) ; Ganjizadeh, A ; Dolatshahi, K. M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
In this paper, a novel computer-vision based methodology is developed for predicting the seismic peak drift ratio of damaged reinforced concrete moment frames using surface crack patterns. A comprehensive database comprising 974 surface crack images from cyclic test results of 256 beam-column joint specimens at various drift ratio levels is collected. The database covers a broad range of concrete compressive strengths, rebar and stirrup strengths, longitudinal and transverse reinforcement ratios, beam and column length to depth ratios, in-plane configurations, and failure modes. Multifractal dimensions of damaged beam-column subassembly images are obtained by the box-counting algorithm to...
Numerical study on the post-earthquake fire behavior of intermediate steel moment frames
, Article Earthquake and Structures ; Volume 22, Issue 2 , 2022 , Pages 137-145 ; 20927614 (ISSN) ; Kazemia, M. T ; Sharif University of Technology
Techno-Press
2022
Abstract
As steel is highly sensitive to temperature variations, fire exposure is more destructive in the case of steel structures in comparison to the concrete ones. The performance of an intermediate three-story steel moment frame with 4 spans was studied under the service load, thermal load and post-earthquake fire in this paper. Also, the effects of passive fire-protection materials such as ordinary cement-based and fire-retardant coatings were investigated. To model and analyze the structure; Abaqus software is utilized. In order to apply the earthquake effect, the push-over analysis method is employed. Changes in the stories deflection, endurance time and growth of nonlinear regions due to...
Seismic Performance of Composite RCS Moment Frames
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
Composite Reinforced Concrete-Steel (RCS) frames which have reinforced concrete columns and steel beams attracted a lot of attention in recent years. They take advantage from the benefits of both reinforced concrete and steel frames thorough using the optimum combination of concrete and steel structural elements. In this research six structures including three 3-story, and three 6-story buildings are designed in a region with very high seismicity risk. These structures include composite RCS moment frames, special steel moment frames, and reinforced concrete special moment frames. RCS moment frames which are designed they not only have reinforced concrete columns similar to reinforced...
Collapse Probability Assessment of Steel Special Moment Resisting Frames through Incremental Dynamic Analysis
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
Assessment of the probability of collapse or exceeding other limit states is one of the major goals of Performance-Based Earthquake Engineering. Moreover, other beneficial materials such as estimation of loss of money and downtime, which make it convenient for decision makers to judge the condition of a structure and take wise steps about it, can be drawn from the results of such an assessment.Current work investigates the probability of collapse and also immediate occupancy limit states at three discrete hazard levels of 50%, 10% and 2% in 50 years and also by utilizing mean annual frequency approach for three archetypes of steel special moment-resisting frames of 4, 8 and 12 stories.Ten...
Seismic Demands on Gravity Only Steel Frames
,
M.Sc. Thesis
Sharif University of Technology
;
Maleki, Shervin
(Supervisor)
Abstract
Nowadays, using perimeter steel moment frames in combination with interior gravity frames have become common practice in structural building design. One of the key benefits of this system is the open space that it provides for the architects. In active seismic regions, special details are required in the design of the seismic force resisting systems to make these frames ductile. However, these details cause excessive displacement for the gravity force resisting system. Although the gravity frames are not designed to endure seismic forces, they collaborate in the system’s response as they are connected to the same floor diaphragm and withstand lateral displacements. Therefore, these systems...